pgsql: Support SQL-compliant triggers on columns, ie fire only if

Log Message:
-----------
Support SQL-compliant triggers on columns, ie fire only if certain columns
are named in the UPDATE's SET list.

Note: the schema of pg_trigger has not actually changed; we've just started
to use a column that was there all along. catversion bumped anyway so that
this commit is included in the history of potentially interesting changes
to system catalog contents.

Itagaki Takahiro

Modified Files:
--------------
pgsql/doc/src/sgml:
catalogs.sgml (r2.209 -> r2.210)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/catalogs.sgml?r1=2.209&r2=2.210)
trigger.sgml (r1.58 -> r1.59)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/trigger.sgml?r1=1.58&r2=1.59)
pgsql/doc/src/sgml/ref:
create_trigger.sgml (r1.50 -> r1.51)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/create_trigger.sgml?r1=1.50&r2=1.51)
pgsql/src/backend/catalog:
index.c (r1.322 -> r1.323)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/index.c?r1=1.322&r2=1.323)
pgsql/src/backend/commands:
tablecmds.c (r1.303 -> r1.304)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tablecmds.c?r1=1.303&r2=1.304)
trigger.c (r1.253 -> r1.254)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/trigger.c?r1=1.253&r2=1.254)
pgsql/src/backend/nodes:
copyfuncs.c (r1.447 -> r1.448)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/copyfuncs.c?r1=1.447&r2=1.448)
equalfuncs.c (r1.369 -> r1.370)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/equalfuncs.c?r1=1.369&r2=1.370)
pgsql/src/backend/optimizer/plan:
setrefs.c (r1.152 -> r1.153)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/plan/setrefs.c?r1=1.152&r2=1.153)
pgsql/src/backend/parser:
gram.y (r2.685 -> r2.686)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/gram.y?r1=2.685&r2=2.686)
pgsql/src/backend/utils/adt:
ruleutils.c (r1.309 -> r1.310)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/ruleutils.c?r1=1.309&r2=1.310)
pgsql/src/bin/pg_dump:
pg_dump.c (r1.551 -> r1.552)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_dump.c?r1=1.551&r2=1.552)
pgsql/src/include/catalog:
catversion.h (r1.545 -> r1.546)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h?r1=1.545&r2=1.546)
pg_trigger.h (r1.34 -> r1.35)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_trigger.h?r1=1.34&r2=1.35)
pgsql/src/include/nodes:
parsenodes.h (r1.409 -> r1.410)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/parsenodes.h?r1=1.409&r2=1.410)
pgsql/src/test/regress/expected:
triggers.out (r1.27 -> r1.28)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/triggers.out?r1=1.27&r2=1.28)
pgsql/src/test/regress/sql:
triggers.sql (r1.16 -> r1.17)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/triggers.sql?r1=1.16&r2=1.17)